Interfering in time-division duplex communication

ABSTRACT

A computer readable storage medium is presented, having computer readable program instructions thereon for causing a processor to carry out the steps of: sub-dividing a time slot into consecutive time intervals, the time slot belongs to multiple time slots allocated to a first node for transmitting to a second node using a wireless time-division duplex communication link between the first node and the second node, the second node transmitting during separate time slots allocated to said second node; and disrupting communication between said first node and said second node by transmitting, using a transmitter, respective interference signals during at least some of said time intervals, each of said interference signals being transmitted on one of said frequency bands, wherein for at least two of said time intervals said interference signals are transmitted on different frequency band.

RELATED APPLICATION

This application is a continuation U.S. patent application Ser. No.16/513,769 filing date Jul. 17, 2019 which claims the benefit ofpriority of Israel Patent Application No. 260726 filed on Jul. 22, 2018,the contents of both are incorporated by reference as if fully set forthherein in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to timedivision duplex communication and, more particularly, but notexclusively, to interfering with time division duplex communication.

In time division duplex (TDD) communication, transmissions by networknodes are separated into different time slots. In some cases, the nodesuse different transmission schemes. For example, one node transmitsfrequency hopping packets whereas a second node transmits fixedfrequency packets during their respective allocated time slots.

Time-division duplexing has a strong advantage in the case where thereis asymmetry of the uplink and downlink data rates. As the amount ofuplink data increases, more communication capacity can be dynamicallyallocated, and as the traffic load becomes lighter, capacity can betaken away.

In some cases, wideband jamming signals are used to disruptcommunication uplink and/or downlink communication. In order tointerfere with Node B's reception of transmissions from Node A, a wideband jamming signal is transmitted towards Node B. The jamming signalmay be a high bandwidth (BW) noise signal (such as white Gaussian noise)or any other wide band signal (such as actual data or a chirp signal).

One disadvantage of wideband jamming solutions is possible interferenceto other communication links in the area. Another disadvantage is lossof power, because the power is distributed over the full bandwidth. Inaddition, jamming solutions do not use a disconnect command and hencecan only cause the two nodes to disconnect by raising the bit error rate(BER) in Node B's reception of Node A.

Another approach to this problem is to transmit a pulsed jamming signalduring the Node A time slot at all the known frequencies used by Node Ain parallel. The disadvantage of the solutions above is still loss ofpower, as the power is distributed over Node A's entire frequency range.Also, as in the previous solution, this jamming technique does notcontain a disconnect command.

Additional background art includes:

-   [1] M. Karlsson et al., “Jamming a TDD Point-to-Point Link Using    Reciprocity-Based MIMO”, IEEE Transactions on Information Forensics    and Security, 12(12), pp. 2957-2970, 11 Jul. 2017.-   [2] International Patent Application Publication No. WO 93/26124.-   [3] K. Grover et al., “Jamming and Anti-jamming Techniques in    Wireless Networks: A Survey”, International Journal of Ad Hoc and    Ubiquitous Computing Volume 17 Issue 4, Pages 197-215, December    2014.-   [4] International Patent Application Publication No. WO 93/22850.-   [5] K. Parlin, “Jamming of Spread Spectrum Communications Used in    UAV Remote Control Systems”, TALLINN UNIVERSITY OF TECHNOLOGY School    of Information Technologies, 2017.

SUMMARY OF THE INVENTION

Embodiments of the invention intend to disconnect and/or interfere withcommunication between nodes in a TDD communication link in which atleast one of the nodes (denoted herein Node A) transmits at differentrespective frequency bands during different times slots allocated to it(i.e. frequency hopping). Transmissions by Node A are interfered with bytransmitting a sequence of high-power short disconnect signals duringeach time slot allocated to Node A. Each disconnect signal istransmitted during a respective time interval within the Node A timeslot. Because the disconnect apparatus transmits over only a single NodeA frequency band at any given time interval, the transmission power ofthe disconnect signal can be maximized at each of the frequency bandsduring a portion of the Node A time slot. Optionally the disconnectsignals are modulated with a disconnect command, which when received byNode B causes Node B to disconnect from Node A. Optionally, thedisconnect signals may be a predefined pattern and/or a noise signalaimed at interfering with the communication between Node A and Node B.

In some embodiments disconnect signals are transmitted over more thanone frequency band during a given time interval. Although in thisembodiment transmission power is divided amongst multiple frequencybands, it is nonetheless higher than it would be if the disconnectsignal covered the entire Node A frequency range.

According to a first aspect of some embodiments of the present inventionthere is provided a method for disconnecting a wireless time-divisionduplex communication link between a first node transmitting during timeslots allocated to the first node and a second node transmitting duringseparate time slots allocated to the second node. The first nodetransmits at differing respective frequency bands during its time slots.The method includes:

sub-dividing a time slot allocated to the first node into consecutivetime intervals; and

transmitting respective disconnect signals during the time intervals.

Each of the disconnect signals is transmitted on a frequency band usedby the first node. The disconnect signals are transmitted on differentfrequency bands during at least two of the time intervals.

According to a second aspect of some embodiments of the presentinvention there is provided an apparatus for disconnecting a wirelesstime-division duplex communication link between a first nodetransmitting during time slots allocated to the first node and a secondnode transmitting during separate time slots allocated to the secondnode. The first node transmits at differing respective frequency bandsduring its time slots. The apparatus includes a signal generator and awireless transmitter. The signal generator sub-divides a time slotallocated to the first node into consecutive time intervals andgenerates respective disconnect signals for multiple time intervals.Each of the disconnect signals occupies a respective one of thefrequency bands. The disconnect signals are on different frequency bandsfor at least two of the time intervals. The wireless transmittertransmits the disconnect signals at the respective time intervals.

According to some implementations of the first aspect or second aspectof the invention, for at least one of the time intervals the disconnectsignal is data modulated.

According to some implementations of the first aspect or second aspectof the invention, for at least one of the time intervals the disconnectsignal is modulated with a disconnect command for the second node.

According to some implementations of the first aspect or second aspectof the invention, for at least one of the time intervals the disconnectsignal is modulated with a pseudo-random data sequence.

According to some implementations of the first aspect or second aspectof the invention, for at least one of the time intervals the disconnectsignal is one of: a predefined jamming signal and a random noise signal.

According to some implementations of the first aspect or second aspectof the invention, transmissions by the second node are monitored and anupcoming time slot of the first node is predicted based on the monitoredtransmissions.

According to some implementations of the first aspect or second aspectof the invention, transmission of the disconnect signals is initiatedwhen a cessation of transmission by the second node is detected.

According to some implementations of the first aspect or second aspectof the invention, transmissions by the second node are analyzed toidentify a disconnection of communication between the first and secondnodes, and when such a disconnection is identified, direct communicationis established with the second node.

According to some implementations of the first aspect or second aspectof the invention, the respective frequency bands are selected from aspecified list of frequency bands.

According to some implementations of the first aspect or second aspectof the invention, disconnect signals are transmitted over an entirefrequency range used by the first node during a single time slot.

According to some implementations of the first aspect or second aspectof the invention, the first node transmits in a known order of thefrequency bands, and the disconnect signals are transmitted in the knownorder. The phase of the order of transmitted disconnect signals ischanged by transmitting one of the disconnect signals at frequency bandout of the known order and continuing subsequent disconnect signaltransmissions in the known order. This phase change may be performedmore than once while interfering with the transmissions.

According to some implementations of the first aspect or second aspectof the invention, the entire frequency range used by the first node isinterfered with by the disconnect signals during a single time slot ofthe first node.

According to some implementations of the first aspect or second aspectof the invention, the respective frequency bands for the disconnectsignals are selected as successive frequency bands over the frequencyrange used by the first node.

According to some implementations of the first aspect or second aspectof the invention, at least two disconnect signals are transmitted inparallel on respective ones of the frequency bands for at least one ofthe time intervals. The number of disconnect signals transmitted inparallel is fewer than a total number of the frequency bands.

According to some implementations of the first aspect or second aspectof the invention, a first sub-set of the frequency bands is transmittedduring a time slot of the first node and a second sub-set of thefrequency hands is transmitted during a subsequent time slot of thefirst node.

According to third aspect of some embodiments of the present inventionthere is provided a method for controlling an apparatus interfering withwireless time-division duplex communication. The time-division duplexcommunication is between a first node transmitting during time slotsallocated to the first node and a second node transmitting duringseparate time slots allocated to the second node. The first nodetransmits at differing respective frequency bands during its time slots.The method includes:

receiving, using a receiver, wireless transmissions from the secondnode;

determining a time slot allocated to the first node based on thereceived transmissions and subdividing the determined time slot intoconsecutive time intervals; and

instructing the apparatus to transmit respective disconnect signalsduring a plurality of the time intervals, each of the disconnect signalsbeing for transmission on a respective one of the plurality of frequencybands, wherein for at least two of the time intervals the disconnectsignals are transmitted on different frequency bands.

According to a fourth aspect of some embodiments of the presentinvention there is provided a controller for a wireless disconnectapparatus for interfering with wireless time-division duplexcommunication link. The time-division duplex communication is between afirst node transmitting during time slots allocated to the first nodeand a second node transmitting during separate time slots allocated tothe second node. The first node transmits at differing respectivefrequency bands during its time slots. The apparatus includes:

a receiver which receives wireless transmissions from the second node;

a signal analyzer which:

-   -   determines a time slot allocated to the first node based on the        received transmissions;    -   subdivides the time slot into consecutive time intervals; and    -   instructs the disconnect apparatus to transmit respective        disconnect signals during a plurality of the time intervals,        each of the disconnect signals being for transmission on a        respective one of the plurality of frequency bands, wherein for        at least two of the time intervals the disconnect signals are        transmitted on different frequency hands.

According to some implementations of the third aspect or fourth aspectof the invention, at least one signal parameter for generation of thedisconnect signals is provided to the apparatus. According to somefurther implementations of the third aspect or fourth aspect of theinvention, the signal parameter includes:

a type of disconnect signal to transmit;

data for modulating onto a disconnect signal;

a duration of the time slot;

respective durations of the time intervals;

the respective frequency bands for the disconnect signals;

respective transmission powers for the disconnect signals; and

a number of disconnect signals to transmit in parallel.

According to some implementations of the third aspect or fourth aspectof the invention, the apparatus is instructed to transmit, on at leastone of the disconnect signals, a disconnect command for disconnectingthe second node from the first node.

According to some implementations of the third aspect or fourth aspectof the invention, disconnection of communication between the first andsecond nodes is detected from the received transmissions and theapparatus is instructed to establish direct communication with thesecond node.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

Implementation of the method and/or system of embodiments of theinvention can involve performing or completing selected tasks manually,automatically, or a combination thereof. Moreover, according to actualinstrumentation and equipment of embodiments of the method and/or systemof the invention, several selected tasks could be implemented byhardware, by software or by firmware or by a combination thereof usingan operating system.

For example, hardware for performing selected tasks according toembodiments of the invention could be implemented as a chip or acircuit.

As software, selected tasks according to embodiments of the inventioncould be implemented as a plurality of software instructions beingexecuted by a computer using any suitable operating system. In anexemplary embodiment of the invention, one or more tasks according toexemplary embodiments of method and/or system as described herein areperformed by a data processor, such as a computing platform forexecuting a plurality of instructions. Optionally, the data processorincludes a volatile memory for storing instructions and/or data and/or anon-volatile storage, for example, a magnetic hard-disk and/or removablemedia, for storing instructions and/or data. Optionally, a networkconnection is provided as well. A display and/or a user input devicesuch as a keyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 illustrates an exemplary scenario for interfering with a TDDcommunication link between nodes A and B;

FIG. 2 is a simplified flow chart of a method for disconnecting awireless time-division duplex communication link, according toembodiments of the invention;

FIGS. 3A-B, 4 and 5 illustrate aggregated disconnect signals used tointerfere with a TDD communication link, according to respectiveexemplary embodiments of the invention;

FIG. 6 is a simplified block diagram of a disconnect apparatus fordisconnecting a wireless time-division duplex communication link,according to embodiments of the invention;

FIGS. 7A-7C illustrate respective timing scenarios for TDD communicationlinks;

FIG. 8 is a simplified flowchart of a method for controlling adisconnect apparatus, according to embodiments of the invention;

FIG. 9 is a simplified block diagram of a controller for a wirelessdisconnect apparatus, according to embodiments of the invention; and

FIG. 10 is a simplified block diagram of a disconnect apparatus,according to an exemplary embodiment of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to timedivision duplex communication and, more particularly, but notexclusively, to interfering with time division duplex communication.

TDD communications links are often used for wireless communicationbetween a controller and an unmanned aerial vehicle (UAV), such as adrone. TDD is particularly suited for this use because of the typicalasymmetry of the uplink communication (from controller to UAV) relativeto the downlink (from UAV to controller).

Embodiments of the invention interfere with a time-division duplexcommunication link between two nodes, in order to disconnect the twonodes. The goal is to perform this disconnection with minimalinterference to other communication links within the area.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings and/or the Examples. The invention iscapable of other embodiments or of being practiced or carried out invarious ways.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

Reference is now made to FIG. 1 , which illustrates an exemplaryscenario for interfering with a TDD communication link between twonodes. Node A 110 transmits frequency hopping packets to Node B 120.Node B 120 transmits fixed frequency packets to Node A 110. Node B 120and Node A 110 transmit in different time frames. Disconnect apparatus130 transmits signals which are received by Node B 120 and are designedto disconnect Node B 120 from Node A 110. Typically, transmissions fromNode B 120 are received by disconnect apparatus 130, but transmissionsfrom Node A 110 are not received and therefore cannot be analyzed bydisconnect apparatus 130.

For clarity, the description herein presents non-limiting exemplaryembodiments in which the TDD communication link is between two nodes(denoted herein Node A and Node B), and in which it is desired todisconnect Node B from Node A. As will be appreciated by the skilledperson, other embodiments of the invention may be implemented for TDDcommunication links with more than two nodes (e.g. a single controllercontrolling multiple drones or multiple controllers controlling multipledrones).

I. Method for Interfering with a TDD Communication Link

Reference is now made to FIG. 2 , which is a simplified flow chart of amethod for disconnecting a wireless time-division duplex communicationlink, according to embodiments of the invention. The time-divisionduplex (TDD) communication link is between a first node (denoted hereinNode A) transmitting during time slots allocated to Node A and a secondnode (denoted herein Node B) transmitting during separate time slotsallocated to Node B.

As used herein the term “separate time slots” means that Node A's timeslots do not overlap with Node B's time slots.

Node A transmits at multiple frequency bands. During each of itsallocated time slots, Node A transmits at a respective one of thesefrequency bands. Node A may transmit in a fixed hop pattern (i.e. in apredetermined repetitive order) or the frequency bands used by Node Atransmission may vary in a different manner. The frequency bands used byNode A should be known or detectable by Node B, so that Node B is ableto receive Node A's transmissions correctly.

In 210, a time slot allocated to the first node is sub-divided intoconsecutive time intervals. Methods for identifying or determining aNode A time slot are described below.

As used herein the term “consecutive time intervals” means that the timeintervals are in a non-overlapping sequence which begins at the start ofthe time slot and ends at the end of the time slot. Optionally the timeinterval duration is the same for each of Node A's time slots.Alternately, some or all of the time slots are divided into differentsequences of time interval durations.

In 220, respective disconnect signals are transmitted during some or allof the time intervals. Each disconnect signal is transmitted on one ofNode A's frequency bands. The disconnect signals are transmitted ondifferent frequency bands during at least two of the time intervals.Optionally, when Node A's frequency bands are not accurately known,disconnect signals are transmitted at frequency bands which are expectedto be used by Node A.

Optionally, during a single Node A time the disconnect signals cover theentire frequency range used by the Node A.

Optionally, the respective frequency bands for the disconnect signalsare selected from a specified list of frequency bands. The list mayinclude frequency bands known to be used by Node A. This approach isbeneficial when Node A does not transmit over a continuous frequencyrange but rather at certain frequency bands within its total frequencyrange.

As used herein the term “aggregated disconnect signal” means the entiredisconnect signal transmitted in a single time slot. The aggregateddisconnect signal is built from the multiple short disconnect signalswhich are transmitted during respective time intervals within a singletime slot. The aggregated disconnect signal may be built in the samemanner for all Node A time slots, or in different manners for differenttime slots. For example, in some Node A time slots the aggregateddisconnect signal may cover Node A's entire frequency range whereas inother time slots only a portion or portions of Node A's frequency rangeis interfered with.

Optionally, a single disconnect signal (i.e. a signal at a singlefrequency band) is transmitted in each time interval, therefore thetransmission power is concentrated in one frequency band.

FIG. 3A illustrates an exemplary embodiment in which Node Atransmissions are interfered with by the staggered transmission of thedisconnect signals during the Node A time slot. The Node A time slot issub-divided into N time intervals. A singe disconnect signal istransmitted during each of the time intervals. If Node A's frequencybands (F1-FN) cover a continuous frequency range, then the aggregateddisconnect signal covers the entire frequency range. If F1-FN areportions of Node A's total frequency range, the aggregated disconnectsignal interferes with all frequency bands used by Node A. In FIG. 3Athe frequency bands of the aggregated disconnect signal are transmittedin the same order during each Node A time slot.

FIG. 3B illustrates an exemplary embodiment in which Node A sendsmultiple packets at different phases but in a constant cycle. As in FIG.3A, the Node A transmissions are interfered with by the staggeredtransmission of the disconnect signals during the Node A time slot.

FIG. 4 illustrates an alternate exemplary embodiment in which the orderof the frequency bands within the aggregated disconnect signal isdifferent for different Node A time slots.

Alternately, during at least one of the time intervals, two or moredisconnect signals are transmitted in parallel. FIG. 5 shows an examplein which the two disconnect signals at different frequency bands aretransmitted during every time interval. Parallel transmission atmultiple frequency bands may be useful when the number of time intervalsavailable in a single Node A time slot is fewer than the number of NodeA frequency bands. In order to cover all of the Node A frequency bandsduring a single Node A time slot, it is necessary to transmit at morethan one frequency band in a given time interval. This technique mayalso be beneficial when the available transmission power is high enoughto interfere with multiple frequency bands in parallel (e.g. when Node Btransmissions are received at a high power indicating that Node B isclose).

Optionally, only a subset of the Node A frequency bands is interferedwith by a disconnect signal during a single Node A time slot and asecond subset of Node A frequency hands is interfered with during adifferent Node A time slot. As above, this may be useful when the numberof time intervals available in a single Node A time slot is fewer thanthe number of Node A frequency bands. This embodiment is also usefulwhen there is some knowledge regarding the possible frequency bands thatNode A may transmit in.

Assigning respective frequency bands to the time intervals in theaggregated time signal may be done by any means known in the art.Embodiments of assigning frequency bands to respective time intervalsinclude but are not limited to:

i) A predefined order;

ii) According to specified rules; and

iii) Randomly.

The assignment may take into account additional information such asknown information about the TDD communication link and/or informationgathered by analyzing transmissions received from Node B.

In some embodiments, Node A transmits in a known hop pattern. Althoughthe order of the frequency bands used by Node A is known, the Node Atransmissions are not received so it is not known which frequency bandis currently being used. This added information may be used to selectthe interference signals. An optional embodiment includes transmittingrapidly changing disconnect signals based on the known hop pattern,using partial frequencies from the list in order to additionallyincrease the disconnect signal power. For example, assume it is knownthat the order of Node A's frequencies is F₁, F₂, F₃, . . . , F_(N).Then F₁, F₂, F₃, F₄ and F₅ may be transmitted together in one aggregateddisconnect signal in parallel with the first Node A packet and F₂, F₃,F₄, F₅ and F₆ may be transmitted together in a second aggregateddisconnect signal in parallel with the second Node A packet. After sometime, if disconnect is not achieved, the next sequence may be changed.

In this way the correct phase is eventually reached with a higher power,as there are fewer disconnect signals required to achieve disconnect.

II. Types of Disconnect Signals

In many TDD communication links a “disconnect command” may be issuedfrom one of the nodes to the other. The disconnect command informs therecipient that the connection is terminated. The receiving node thenterminates its side of the connection. In some cases, the nodes willthen try to reestablish their connection in the same or in anothertiming phase. It is possible to disturb this type of communication bytransmitting a disconnect signal carrying a disconnect command to NodeB. When the disconnect signal is received by Node B at a highersignal-to-noise ratio (SNR) than the Node A packets, Node B maydemodulate the disconnect signal instead of the packet sent by Node A.This causes the link between Node A and Node B to be broken.

Optionally, during at least one of the time intervals the disconnectsignal is a data modulated carrier signal. Further optionally, thedisconnect signal carries one or more data packets constructed inaccordance with the TDD communication link protocol.

Optionally, one or more of the disconnect signals are modulated with adisconnect command or commands for Node B. The disconnect command isbuilt according to the known protocol between Node A and Node B. Thedisconnect signal is typically a short signal, preferably shorter thanT_(A)/N (T_(A) is Node A slot time and N is the number of knownfrequencies). If the shortest disconnect signal time T_(dis) is longerthan T_(A)/N, then in order to cover all the Node A frequencies it isnecessary to transmit k=floor(N·T_(dis)/T_(A)) parallel disconnectsignals.

In some cases, such as when the disconnect length is too long or theprotocol between Node A and Node B is not known, a different type ofdisconnect signal may be used. In this case the disconnection isachieved by reducing the SNR of the reception of Node A signal by NodeB. This causes a high bit error rate (BER) that will eventually fail thewhole packet or frame due to failure in the parity check.

Other types of disconnect signals include but are not limited to:

a) A noise signal, such as a predefined noise pattern, random noise orwhite Gaussian noise signal;

b) A predefined jamming signal;

c) A modulated pseudo-random binary sequence, optionally using aconstant envelope such as BPSK; and

d) A predefined binary sequence modulated as a constant envelope signal(such as any phase shift keying signal).

Using a noise or PSK disconnect signal is beneficial when Node B cannotreceive a packet from the disconnect signal due to the parallelreception of Node A's packet).

The aggregated disconnect signal for a single time slot may be expressedas:J(T)=N(t)·cos(2πf(t)t+ϕ)where N(t) is the aggregated disconnect signal, f(t) is the carrierfrequency and ϕ is a constant or random phase. Optionally, N(t) is oneof:

-   -   i) A sequence of M packets containing the protocol specific        command to disconnect; and    -   ii) A predefined pattern (such as White Gaussian Noise,        modulated Pseudo Random Binary Sequence, any modulated binary        sequence or any predefined jamming signal).

Regarding Node A's changing carrier frequency f (t):

A) In embodiments in which the disconnect signal carrier frequencies area linear series {f₀+n·Δf}:

${{f(t)} = {f_{0} + {\Delta{f \cdot {\sum\limits_{n = 1}^{N - 1}{u( {t - T_{n}} )}}}}}}{T_{n} = {T_{packet} \cdot \frac{n}{N}}}{{u(t)} = \{ \begin{matrix}{{1{if}t} > 0} \\{0{otherwwise}}\end{matrix} }$B) In embodiments in which the disconnect signal carrier frequencies areselected from a list {f_(n)}:

$\begin{matrix}{{f(t)} = {\sum\limits_{m = 0}^{M - 1}{f_{n} \cdot \{ {{u( {t - T_{n}} )} - {u( {t - T_{n + 1}} )}} \}}}} & \end{matrix}$

As shown in FIG. 4 , the order of the frequencies within the aggregateddisconnect signal may be different for transmissions in different timeslots.

III. Disconnect Apparatus

Reference is now made to FIG. 6 , which is a simplified block diagram ofa disconnect apparatus for disconnecting a wireless time-division duplexcommunication link, according to embodiments of the invention. Asdescribed above, the TDD communication link is between Node A whichtransmits at differing respective frequencies during its allocated timeslots and Node B which transmits at a fixed frequency during its timeslots.

Disconnect apparatus 600 includes signal generator 610 and wirelesstransmitter 620.

Signal generator 610 generates the aggregated disconnect signal for eachNode A time slot by sub-dividing a time slot allocated to the first nodeinto consecutive time intervals and generating respective disconnectsignals for multiple time intervals. Each of the disconnect signalsoccupies a respective one of the Node A frequency bands, where during atleast two of the time intervals the disconnect signals occupy differentfrequency bands.

In order to interfere with communications between Node A and Node B, theaggregated disconnect signal generated by signal generator 610 istransmitted by transmitter 620 during the respective Node A time slot,in parallel with the Node A transmissions.

As will be appreciated by the skilled person, signal generator 610 maybe used to generate any of the disconnect signals and aggregatedisconnect signals described herein, as required for a specificembodiment. For example, in some embodiments more than one disconnectsignal (at different respective frequency bands) are transmitted duringa single time interval.

Optionally, for at least one of the time intervals the disconnect signalis a carrier frequency in the respective frequency band, where thecarrier signal is modulated with one of:

-   -   a) a disconnect command for the second node (or one of several        options of disconnect commands, if several exist);    -   b) A noise signal, such as a predefined noise pattern, random        noise or white Gaussian noise signal;    -   c) A predefined jamming signal;    -   d) A pseudo-random binary sequence, optionally using a constant        envelope such as BPSK; and    -   e) A predefined binary sequence (modulated as a constant        envelope signal, for example any phase shift keying signal).

Optionally, during a given time slot signal generator 610 selects therespective frequency bands for the disconnect signals from a list ofknown frequency bands used by the Node A. Alternately or additionally,during a given time slot signal generator 610 selects the respectivefrequency bands for the disconnect signals as successive frequency bandsover a frequency range used by Node A.

Optionally, during a single Node A time slot the entire frequency rangeused by the Node A is interfered with by the disconnect signals.

In the embodiment of FIG. 6 , signal generator 610 and transmitter 620are a single apparatus. In alternate embodiments, signal generator 610is an add-on unit which provides the aggregated disconnect signals to astandalone transmitter.

IV. Monitoring Node B Communications

Optionally, Node B communications are monitored and analyzed in order togather information about communication between Node A and Node B and/orparameters of the TDD communication link. The Node B transmissions maybe monitored and/or analyzed continuously or intermittently.

Several Node B transmissions may be collected and analyzed in order topredict upcoming Node A time slots. The prediction may also be based onprior knowledge, such as that Node A is transmitting packets in a fixedcycle or that Node A is transmitting several packets in a fixed cycle(e.g. at 10n msec and at 10n+4 msec, which are two phases with a 10 mseccycle).

Types of information that may be obtained by this analysis include butare not limited to:

1) Identifying a disconnection between Nodes A and B. Optionally, whenthe disconnection is identified direct communication is established withNode B (for example by sending Node B a request to connect);

2) Identifying and/or predicting time slot(s) allocated to Node A and/orNode B. Knowledge of the start and/or stop times of the time slotsenables transmitting the disconnect signals at the correct time;

3) The communication protocol used by Nodes A and B; and

4) The management of the Node A and Node B time slots (e.g. see FIGS.7A-7C).

It is desired to transmit the aggregated disconnect signal during theNode A time slot for which it was built. Many ways of allocating timeslots in TDD are known in the art. The embodiments presented herein arenot limited to any particular type of slot allocation by the TDDcommunication link.

Alternately or additionally, the beginning of a Node A time slot isdetected when Node B sends a request to reconnect. Node B transmissionsare optionally analyzed to determine the protocol used by the TDDcommunication link, so that the request to reconnect may be identifiedin the Node B transmissions.

The decision when to begin transmission of the aggregated disconnectsignal may be based on more of:

1) Detecting the beginning and/or end of Node B transmissions. SeveralNode B transmissions may be collected and analyzed together in order to“learn” the time slot pattern and predict an upcoming Node A time slot(e.g. transmission packet time) in advance. This may block signals (suchas ACK responses) that are transmitted by Node A at the beginning of itstime slot.

2) Identifying the transmission of data sent by Node B (such as arequest to reconnect, an ACK packet, a disconnect command, etc.).

3) Prior knowledge of the access scheme.

Exemplary embodiments include:

1) The aggregated disconnect signal is transmitted a predefined timeafter the Node B transmission ends. This approach is effective when NodeB is the master and manages the time frames and Node A responds to NodeB, as illustrated in FIG. 7A.

2) The aggregated disconnect signal is transmitted a predefined timebefore a predicted Node B time slot. This approach is effective in thetiming scenarios illustrated in FIGS. 7B and 7C. In FIG. 7B, Node A isthe master and Node B responds to Node B, typically after a relativelyshort buffer time. FIG. 7C illustrates the case where the cycle time, T,and slot times, T_(A) and TB, are determined in advance, for examplewhen the link is created. If this pattern is known, once a Node A orNode B time slot is identified the timing of future time slots is known.

V. Controlling a Disconnect Apparatus

Reference is now made to FIG. 8 , which is a simplified flowchart of amethod for controlling a disconnect apparatus interfering with wirelesstime-division duplex communication, according to embodiments of theinvention. This control is based on information gathered by receivingand analyzing signals transmitted by Node B.

In 810, wireless transmissions are received from Node B.

In 820, an upcoming Node A time slot is determined based on the receivedtransmissions. Optional techniques for performing this determination aredescribed above (e.g. identifying the end of a Node B time slot, byprior knowledge of the timing of the time slots, etc.).

In 830, the upcoming Node A time slot is subdivided into consecutivetime intervals.

In 840, the disconnect apparatus is instructed to transmit, during theNode A time slot determined in 820, an aggregated disconnect signal isbuilt based on the respective frequency bands assigned to time intervalswithin the time slot. The frequency band assignment may be designed toyield any type or types of aggregated disconnect signals describedherein, as required for a specific embodiment.

Optionally, the instructions to the disconnect apparatus include atleast one signal parameter for generation of the disconnect signals.Signal parameters for generating the disconnect signals include but arenot limited to:

i) Type of disconnect signal to transmit;

ii) Data for modulating onto the disconnect signal;

iii) The duration of the time slot;

iv) Respective durations of the time intervals;

v) Respective frequency bands for the disconnect signals;

vi) Respective transmission powers for the disconnect signals; and

vii) The number of disconnect signals to transmit in parallel.

Optionally, the disconnect apparatus is instructed to modulate adisconnect command onto at least one of the disconnect signals.

Optionally, the method further includes detecting that Node A and Node Bare disconnected (e.g. the TDD communication link has been successfullyinterfered with). The disconnect apparatus is then instructed toestablish direct communication with the Node B. Optionally,communication is established with Node B by transmitting a request toconnect with Node B at high power.

VI. Controller for Disconnect Apparatus

Reference is now made to FIG. 9 , which is a simplified block diagram ofa controller for a wireless disconnect apparatus, according toembodiments of the invention. Controller 900 includes receiver 910 andsignal analyzer 920, which together implement the method shown in FIG. 8.

Receiver 910 receives wireless transmissions from the Node B. Signalanalyzer 920 analyzes the received signals to determine an upcoming timeslot allocated to Node A and to subdivide the Node A time slot intoconsecutive time intervals. Signal analyzer 920 also instructs thedisconnect apparatus how the aggregated disconnect signal should bebuilt and when it should be transmitted.

Optionally, receiver 910 performs analog and/or digital processing onthe received signal before providing it signal analyzer 920. Forexample, receiver 910 may include an analog-to-digital converter whichconverts the received Node B signal to a digital signal which isanalyzed by signal analyzer 920.

In the embodiment of FIG. 9 , receiver 910 and signal analyzer 920 are asingle apparatus. In alternate embodiments, signal analyzer 920 is anadd-on unit which provides the aggregated disconnect signals to astandalone transmitter.

VII. Exemplary Disconnect Apparatus

Reference is now made to FIG. 10 , which is a simplified block diagramof a disconnect apparatus, according to an exemplary embodiment of theinvention. Disconnect apparatus 1000 includes the components shown inFIGS. 6 and 9 . Receiver 1010 receives signals transmitted by Node B.Signal analyzer 1020 analyzes the received signals, determines anupcoming Node A time slot and/or decides how the aggregated disconnectsignal should be built for the Node A time slot. These instructions areprovided to signal generator 1030, which generates the aggregateddisconnect signal for transmission by wireless transmitter 1040.

The combined operation of signal analyzer 1020 and signal generator 1030may perform any of the analyses described herein and generate any of thedisconnect signals and aggregated disconnect signals described herein.For brevity, the complete details of all possible embodiments are notrepeated but they are encompassed by disconnect apparatus 1000.

In the embodiment shown in FIG. 10 , receiver 1010, signal analyzer1020, signal generator 1030 and transmitter 1040 form a singleapparatus. In alternate embodiments, the receiver and/or transmitter areexternal.

The methods as described above are used in the fabrication of integratedcircuit chips.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

It is expected that during the life of a patent maturing from thisapplication many relevant TDD communication links, communicationprotocols and nodes communicating over a TDD communication link will bedeveloped and the scope of the term TDD, TDD communication link,protocol and node is intended to include all such new technologies apriori.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

The term “consisting of” means “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 6, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 6, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may al so be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present invention. To the extent thatsection headings are used, they should not be construed as necessarilylimiting. In addition, any priority document(s) of this applicationis/are hereby incorporated herein by reference in its/their entirety.

We claim:
 1. A non-transitory computer readable storage medium havingcomputer readable program instructions thereon for causing a processorto carry out the steps of: sub-dividing a time slot into consecutivetime intervals, the time slot belongs to multiple time slots allocatedto a first node for transmitting to a second node using a wirelesstime-division duplex communication link between the first node and thesecond node, the second node transmitting during separate time slotsallocated to said second node; and disrupting communication between saidfirst node and said second node by transmitting, using a transmitter,respective interference signals during at least some of said timeintervals, each of said interference signals being transmitted on one ofsaid frequency bands, wherein for at least two of said time intervalssaid interference signals are transmitted on different frequency bands.2. A non-transitory computer readable storage medium according to claim1, wherein for at least one of said time intervals said interferencesignal is data modulated.
 3. A non-transitory computer readable storagemedium according to claim 1, wherein for at least one of said timeintervals said interference signal is modulated with a disconnectcommand for said second node.
 4. A non-transitory computer readablestorage medium according to claim 1, wherein for at least one of saidtime intervals said interference signal is modulated with apseudo-random data sequence.
 5. A non-transitory computer readablestorage medium according to claim 1, wherein for at least one of saidtime intervals said interference signal comprises one of: a predefinedjamming signal; and a random noise signal.
 6. A non-transitory computerreadable storage medium according to claim 1, having computer readableprogram instructions thereon for further causing the processor to carryout the steps of: monitoring transmissions by said second node; andpredicting an upcoming time slot of said first node based on saidmonitored transmissions.
 7. A non-transitory computer readable storagemedium according to claim 1, having computer readable programinstructions thereon for further causing the processor to carry out thesteps of initiating said transmitting of said interference signals whena cessation of transmission by said second node is detected.
 8. Anon-transitory computer readable storage medium according to claim 1,having computer readable program instructions thereon for furthercausing the processor to carry out the steps of analyzing transmissionsby said second node to identify a disconnection of communication betweensaid first and second nodes; and when said disconnection is identified,establishing direct communication with said second node.
 9. Anon-transitory computer readable storage medium according to claim 1,having computer readable program instructions thereon for furthercausing the processor to carry out the steps of selecting saidrespective frequency bands from a specified list of frequency bands. 10.A non-transitory computer readable storage medium according to claim 1,wherein, during a single time slot, interference signals are transmittedover an entire frequency range used by said first node.
 11. Anon-transitory computer readable storage medium according to claim 1,wherein said first node transmits in a known order of said frequencybands, wherein the computer readable storage medium having computerreadable program instructions thereon for further causing the processorto carry out the steps of: transmitting said interference signals insaid known order; and changing a phase of said order of transmittedinterference signals by transmitting one of said interference signals atfrequency band out of said known order and continuing subsequentinterference signal transmissions in said known order.
 12. Anon-transitory computer readable storage medium according to claim 1,wherein an entire frequency range used by said first node is interferedwith by said interference signals during a single time slot of saidfirst node.
 13. A non-transitory computer readable storage mediumaccording to claim 1, having computer readable program instructionsthereon for further causing the processor to carry out the steps oftransmitting, for at least one of said time intervals, at least twointerference signals in parallel on respective ones of said frequencybands, wherein a number of interference signals transmitted in parallelis fewer than a total number of said frequency bands.
 14. Anon-transitory computer readable storage medium according to claim 1,having computer readable program instructions thereon for furthercausing the processor to carry out the steps of transmitting a firstsub-set of said frequency bands during said time slot of said first nodeand a second sub-set of said frequency bands during a subsequent timeslot of said first node.
 15. A non-transitory computer readable storagemedium having computer readable program instructions thereon for causinga processor to carry out the steps of: receiving, using a receiver,wireless transmissions, from a second node; wherein the second nodecommunicates with a first node by time-division duplex communication,wherein the first node transmitting during time slots allocated to saidfirst node and the second node transmitting during separate time slotsallocated to said second node, said first node transmitting at arespective one of a plurality of frequency bands during each of saidtime slots allocated to said first node; determining a time slotallocated to said first node, out of the time slots allocated to saidfirst node, the determining is based on said received transmissions;subdividing said determined time slot into consecutive time intervals;and instructing an apparatus interfering with said time-division duplexcommunication to transmit respective interference signals during aplurality of said time intervals, each of said interference signalsbeing for transmission on a respective one of said plurality offrequency bands, wherein for at least two of said time intervals saidinterference signals are transmitted on different frequency bands.
 16. Anon-transitory computer readable storage medium according to claim 15,having computer readable program instructions thereon for furthercausing the processor to carry out the steps of providing to saidapparatus at least one signal parameter for generation of saidinterference signals.
 17. A non-transitory computer readable storagemedium according to claim 16, wherein said at least one signal parametercomprises: a type of interference signal to transmit; data formodulating onto an interference signal; a duration of said time slot;respective durations of said time intervals; said respective frequencybands for said interference signals; respective transmission powers forsaid interference signals; and a number of interference signals totransmit in parallel.
 18. A non-transitory computer readable storagemedium according to claim 15, wherein said instructing comprisesinstructing said apparatus to transmit, on at least one of saidinterference signals, a disconnect command for disconnecting said secondnode from said first node.
 19. A non-transitory computer readablestorage medium according to claim 15, having computer readable programinstructions thereon for further causing the processor to carry out thesteps of: detecting, from said received transmissions, a disconnectionof communication between said first and second nodes; and instructingsaid apparatus to establish direct communication with said second node.